Cure in place thermal interface material

ABSTRACT

Methods and devices for providing an even distribution of waste heat in a vehicular battery pack, including a battery pack, a cold plate, a coolant reservoir, a support structure between the battery pack and the coolant reservoir, and a conformable thermal interface material for filling the space between cells of the battery pack and the coolant reservoir so as to provide thermal contact between the cells and the coolant reservoir for distributing the waste heat. In addition, methods and devices for providing an even distribution of waste heat and structural support in any heat source to heat sink for applications such as small devices such as computer motors.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of and claims the benefit of priority toU.S. patent application Ser. No. 14/990,189, filed Jan. 7, 2016, whichis hereby incorporated by reference in its entirety.

FIELD

This application relates generally to distribution of waste heat in avehicular battery pack. More specifically, the application relates tomethods and devices for allowing the even distribution of the waste heatin the vehicular battery pack or other applications that require heatdistribution via a conformable thermal interface material.

BACKGROUND

Battery powered vehicles offer significant advantages over traditionalmodes of travel. However, multiple technological problems still need tobe overcome so as to ensure optimal use of the technology. Currentmarket products are limited, for example, by range of travel, structuralsoundness, and inefficient removal of the waste heat from the batterypacks.

Current systems for battery pack waste heat removal are limited bytechnological problems, often suffering from brittle materials,cracking, and ineffective contacts that hinder heat transfer.Additionally, there are limits in that currently utilized materials maypoorly conform to build variation.

There is a long-felt need in the art for novel systems and methodsproviding for heat transfer where constant contact between componentscan be maintained, using materials that meet varying designs and haveeffective thermal properties so as to provide reliable transfer of thewaste heat from the cells of the battery packs.

SUMMARY

Embodiments described herein detail a system for providing an evendistribution of waste heat in the vehicular battery pack. The system caninclude the battery pack, at least one cold plate extending between twocells of the battery pack, and a coolant reservoir coupled to the coldplate via the conformable thermal interface material such that heat canbe conducted therebetween. A cold plate can comprise aluminum. Inspecific embodiments there is a support structure between the batterypack and the coolant reservoir, and the conformable thermal interfacematerial in the form of a liquid or a gel (or a paste or which includesa paste) is placeable within the support structure. The thermalinterface material can be a liquid polymer and/or a liquid gel. Theconformable thermal interface material can be configured to be flowableso as to fill space between the reservoir and each cell of the batterypack such that there is constant thermal contact between an entire lowersurface of each of the cells of the battery pack and a top surface ofthe coolant reservoir. Upon flowing into the space the conformablethermal interface material can be, for example, from about two to aboutfive millimeters thick, or from about six to about twenty-fivemillimeters thick. In specific embodiments the conformable thermalinterface material maintains the constant thermal contact uponcross-linking, which decreases the flowability of the conformablethermal interface material and provides for the even distribution of thewaste heat via conduction of the waste heat from each of the cells ofthe battery pack to the coolant reservoir. Cross-linking can beperformed thermally and/or photochemically. Methods of cross-linking canalso include chemical cross-linking such as peroxide curing and catalystaddition; other cross-linking methods include ultraviolet and lasercross-linking.

Additional embodiments described herein provide for a method forproviding an even distribution of waste heat from the battery pack inthe vehicle via the conformable thermal interface material. Specificembodiments include providing the coolant reservoir and the supportstructure coupled to the reservoir, and placing the conformable thermalinterface material in the form of the liquid or the gel within thesupport structure. Specific embodiments include placing the bottomsurface of the battery pack into the liquid and/or the gel such that theliquid and/or the gel flows around each of the cells of the battery packsuch that there is constant thermal contact between the entire lowersurface of each of the cells of the battery pack and a surface of thecoolant reservoir. The method can also include cross-linking theconformable thermal interface material thereby decreasing theflowability of the conformable thermal interface material and providingfor the even distribution of the waste heat via conduction of the wasteheat from each of the cells to the coolant reservoir. The liquid or thegel can be used independently or together, and can contain a polymer,and cross-linking can be partial (such about one to about fifty percent)or complete (approximately one-hundred percent). In specific embodimentsthe cold plates can be coupled to the battery pack prior to introductionof the conformable thermal interface material into the supportstructure.

BRIEF DESCRIPTION OF THE FIGURES

The following detailed description of specific embodiments can be bestunderstood when read in conjunction with the following drawings, wherelike structure is indicated with like reference numerals and in which:

FIG. 1 illustrates a schematic diagram of an embodiment of a system forproviding the even distribution of the waste heat in the vehicularbattery pack demonstrating the conformable thermal interface material;

FIG. 2 illustrates a cross-section of the system of FIG. 1 along line2-2 of FIG. 1;

FIG. 3 illustrates example embodiments of cold plate shapes;

FIG. 4 illustrates the vehicle that can contain therein one or more ofthe cells of one or more of the battery packs; and

FIG. 5 illustrates the use of embodiments in an application wherethermal distribution is required for a small heat sink to an externalheat sink.

The embodiments set forth in the drawings are illustrative in nature andare not intended to be limiting of the embodiments defined by theclaims. Moreover, individual aspects of the drawings and the embodimentswill be more fully apparent and understood in view of the detaileddescription that follows.

DETAILED DESCRIPTION

Specific embodiments of the present disclosure will now be described.The invention may, however, be embodied in different forms and shouldnot be construed as limited to the embodiments set forth herein. Rather,these embodiments are provided so that this disclosure will be thoroughand complete, and will fully convey the scope of the invention to thoseskilled in the art.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which embodiments of this invention belong. The terminologyused herein is for describing particular embodiments only and is notintended to be limiting of the invention. As used in the specificationand appended claims, the singular forms “a,” “an,” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise.

Unless otherwise indicated, all numbers expressing quantities ofingredients, properties such as molecular weight, reaction conditions,and so forth as used in the specification and claims are to beunderstood as being modified in all instances by the term “about,” whichis intended to mean up to ±10% of an indicated value. Additionally, thedisclosure of any ranges in the specification and claims are to beunderstood as including the range itself and also anything subsumedtherein, as well as endpoints. Unless otherwise indicated, the numericalproperties set forth in the specification and claims are approximationsthat may vary depending on the desired properties sought to be obtainedin embodiments of the present invention. Notwithstanding that numericalranges and parameters setting forth the broad scope of embodiments ofthe invention are approximations, the numerical values set forth in thespecific examples are reported as precisely as possible. Any numericalvalues, however, inherently contain certain errors necessarily resultingfrom error found in their respective measurements.

Parts of methods described herein such as mathematical determinations,calculations, inputting of data for computations or determinations ofequations or parts thereof can be performed on parts of or one or morecomputers or computer systems that can include one or more processors,as well as software to run or execute programs and run calculations orcomputations.

Methods and systems and parts thereof described herein can be combinedso as to implement embodiments of the invention. Forms of words usedherein can have variations: for example when a word such as “couple” isused, this implies that variations such as “coupled to,” and “coupling,”and “coupling to” are understood to have been considered. When termssuch as “formula,” “formulate” and “formulation” are used, all forms ofsuch words have been considered for methods and systems herein.

Within the present context, as used herein, “vehicle” can include a car,truck, van sport utility vehicle (SUV) or the like, and can be allelectric, or can include other forms of power such as one or moreconventional engines, such one or more internal combustion engines.

FIG. 1 illustrates a schematic diagram of an embodiment of the system 1for providing an even distribution of waste heat in the vehicularbattery pack demonstrating the conformable thermal interface material 4.Also illustrated is the cell 2 of the battery pack; seven cells 2 areshown forming a battery pack, though there can be other numbers of cells2, such as about one to about ten, or from about one to about thirty, ormultiple battery packs of varying numbers of cells 2. Also illustratedis foam 3, such as a strip or strips that can extend between the cells2, the cold plate top portion 5 (also herein called a solid fin), thecoolant reservoir 6, the support structure 7, and the cold plate bottomportion 8. The coolant-in location 9 is illustrated, as is thecoolant-out 10 location. In specific embodiments the coolant reservoir 6has a convective coolant flow in the direction of arrow 11. In specificembodiments the direction of flow can be in the opposing direction. Across-section of the system of FIG. 1 along line 2-2 is illustrated inFIG. 2. Also illustrated are the cell 2, the coolant reservoir 6, thecold plate bottom portion 8, and the conformable thermal interfacematerial 4 which in specific embodiments flows above and below the coldplate bottom portion 8. In specific embodiments the coolant reservoircarries ethylene glycol mixtures and/or other cooling fluids such asorganic refrigerants, phase change materials (such as ammonia) or shortchained alcohols (for example, ethanol and/or methanol). If cooled, bygases, air or nitrogen can be used. Flow rates vary depending on coolingmedia. Typical flow rates for liquids are 10 liters per minute, aircooling rates are typically 200-300 m³/hr. Temperatures for steady statecan be about 25 degrees Celsius or less). One or more of the cold platescan have an approximate “L-shape” (FIG. 1) where the bottom portion ofthe cold plate 8 has a length at the bottom of the “L-shape” (and inline with a longitudinal axis of the coolant reservoir 6) and the topportion 5 of the cold plate has a length at the top of the “L-shape”(and extends between and/or along the outer edge of one or more of thecells 2 along a plane in line with the direction of the cell's height).There can be one or more than one cold plates, such as four or more asshown. A technical difficulty in the art includes getting the coldplates aligned, and embodiments provided herein provide approximatelyone-hundred percent contact between each of the cells 2 and the coolantreservoir 6 when the cold plates are perfectly aligned (such that thebottom portions 8 of the cold plates form a single plane) as well aswhen they are not. Regarding the conformable thermal interface material4, this can flow such that it is all around the bottom portion 8 of oneor more of the cold plates, as well as a portion of the top portion 5 ofthe cold plate. FIG. 3 illustrates example embodiments of cold plateshapes, such as a split-shape 12, spring-fin 13, traditional 14, andwave plate 15; embodiments can have one, more than one, or all of theshapes in a single system 1.

FIG. 4 illustrates the vehicle 16 that can contain therein one or moreof the cells 2 of one or more of the battery packs. The battery pack orpacks can be located in the front, middle, or rear of the car. Thebattery pack or packs can be coupled to the bottom of the car.Additionally, systems 1 outlined herein can involve cooling in computerapplications within and/or outside of the vehicle 16, where thermalconduction is required between interfaces. In specific embodiments thevehicle includes use of the conformable thermal interface material 4within a system 1 providing power to the vehicle 16, and also includesthe thermal interface material 4 within a computer system having a powersource and controlling an aspect of the car other than propulsion. FIG.5 illustrates the use of embodiments in an application where thermaldistribution is required for a small heat sink to an external heat sink.Illustrated are a heat source 17, such as a motor, a heat sink 18, and asolid structural interface 19. The solid structural interface 19 cancomprise the conformable thermal material 4, which acts as a thermalconductor moving heat away from the source 17 to the solid structuralinterface 19.

In specific embodiments of systems and methods described herein, thethermal conducting material is part of a formulation comprising theconformable thermal interface material (herein thermal conducting andthermal spreading are terms used synonymously). The formulation caninclude a combination of one or more of: a condensation polymer(polyvinylidene fluoride, poly(di-methyl siloxane), etc.), a processingaid (fluorosurfactant perfluorononanoic acid), and/or a thermaldissipating agent (such as boron nitride, though this can be used incombination with one or more ceramics) to spread the heat from affectedareas in a coating, and a flame retardant

The formulations can include one or more (or all) of: a thermallyconductive silicone mixture, a thermally conductive epoxy mixture, athermally conductive Alkyd resin with a styrene solvent mixture, athermally conductive Kynar® resin, a thermally conductive glue, and/or athermally conductive polyoctenamer, as outlined below. Some resinsdescribed could be loaded with graphite and/or aluminum powders and givehigh thermal conductivity but can be electrically conductive as wellwhich can entail the use of electrically conductive powders such asgraphite, carbon black, aluminum, copper, zinc, silver, or mixturesthereof. The formulations can include one or more of parts or all of theexamples provided in the text that follows.

Thermally Conductive Silicone Mixture (That can Include Quick-Sil®)

This mixture is a two part room temperature vulcanizing (RTV) siliconerubber that has a 1 to 2 minute working time and cures in approximately15 minutes. Part A (or Part B) is kneaded at between 5 and 50 wt.percent (and preferably 33 wt. %) in specific embodiments with alumina,synthetic diamond or boron nitride powder (based on total resin solids)as a thermally conductive additive. Part B (or Part A) is then kneadedquickly with the second component and the putty material is quickly usedas a potting material to protect automotive battery cells. Theconductive silicone produces 100% solids, tough, strong, flexible, andlong-lasting molds with 0% shrinkage.

Thermally Conductive Epoxy Mixture

This mixture is a two-part epoxy resin system (Such as one or more ofMasterBond®, Loctite®, Gorilla®, or 3M®, etc.) consisting of an epoxyresin and hardener that can be kneaded as an individual component or asa mixture of the components with between 5 and 50 wt. percent (andpreferably 33 wt. %) in specific embodiments with alumina, syntheticdiamond or boron nitride powder (based on total resin solids) as athermally conductive additive. The putty material can be quickly used asa potting material to protect automotive battery cells. The thermallyconductive epoxy resin produces 100% solids, tough, strong, flexible,and long-lasting molds with low shrinkage.

Thermally Conductive Alkyd Resin with Styrene Solvent Mixture

This mixture is an unsaturated polyester (such as a fumaricacid-ethylene glycol based polyester or a propoxylated bisphenol-Afumarate resin) or other styrene soluble alkyd polyester resins (3M®,Kao®, Oxychem®, etc.) that can be mixed with styrene monomer to form apaste and then methylethylketone peroxide is added. The putty can bekneaded at between 5 and 50 wt. percent (and preferably 33 wt. %) inspecific embodiments with alumina, synthetic diamond or boron nitridepowder (based on total resin solids) as a thermally conductive additive.The putty material can be quickly used as a potting material to protectautomotive battery cells. The thermally conductive mixture produces 100%solids, tough, strong, flexible, and long-lasting molds with lowshrinkage.

Thermally Conductive Kynar® Resin

This resin is a polyvinylidene fluoride copolymer (Arkema®, Kynar® 2751)that can be mixed with acetone (50 wt. % solids) to form a paste andthen is kneaded at between 5 and 50 wt. percent (and preferably 33 wt.%) in specific embodiments with alumina, synthetic diamond or boronnitride powder (based on total resin solids) as a thermally conductiveadditive. The putty material can then be used as a potting material toprotect automotive battery cells. The thermally conductive mixtureproduces tough, strong, flexible, and long-lasting molds with lowshrinkage.

Thermally Conductive Booger Glue®

A brick of Booger Glue® or credit card glue (polyisobutylene) can bekneaded at between 5 and 50 wt. percent (and preferably 33 wt. %) inspecific embodiments with alumina, synthetic diamond or boron nitridepowder (based on total resin solids) as a thermally conductive additive.The mixture can then used as a potting material to protect automotivebattery cells. The thermally conductive mixture produces 100% solids,tough, strong, flexible, and long-lasting molds with low shrinkage.

Thermally Conductive Polyoctenamer

Cyclooctene (Aldrich) and a catalyst are in specific embodimentscombined at between 5 and 50 wt. percent (and preferably 33 wt. %) inspecific embodiments with alumina, synthetic diamond or boron nitridepowder (based on total resin solids) as a thermally conductive additive.The catalyst in specific embodiments is a ring opening metathesispolymerization catalyst (such as Grubb's® catalyst). The mixture canthen be used as a potting material to protect automotive battery cells.The thermally conductive mixture produces 100% solids, tough, strong,flexible, long-lasting, and rubbery molds with no shrinkage.

Pastes can be utilized, and example thermal conductivities of examplepastes are provided in Table 1, below. In specific embodiments thethermal conductivity of the paste is about 2.5 Watt/m·K. In specificembodiments, the conductivity can be between about 2.5 and about 11.3Watt/m·K.

TABLE 1 Thermal conductivity, Material Watt/m · K Silicone with 10%boron nitride 4.28 Silicone with 33% boron nitride 5.54 Silicone with50% boron nitride 8.58 Kynar ® with 50% boron nitride 7.92 Alkyd Resinwith Styrene Solvent Mixture with 33% 7.18 boron nitride Alkyd Resinwith Styrene Solvent Mixture with 33% 10.03 synthetic diamond (3.5micron) Alkyd Resin with Styrene Solvent Mixture with 33% 11.3 (equalweights of synthetic diamond + boron nitride)

The conformable thermal interface material can be part of a formulationcomprising one or more of polyvinylidene fluoride, boron nitride,melamine, a processing aid, and a ceramic. In specific embodiments, theformulation comprises, by weight fraction: from about 0.65 to about 0.75polyvinylidene fluoride; from about 0.10 to about 0.15 boron nitride;from about 0.05 to about 0.10 melamine; and from about 0.05 to about 0.1the processing aid and the ceramic combined. In specific embodimentsboron nitride is used having a heat transfer coefficient of about 1700watts per square meter Kelvin. Other materials such as synthetic diamondand an aluminum oxide can be used as well.

In yet other embodiments of systems and methods described herein, theconformable thermal interface material is part of a formulationcomprising one or more of polydimethylsiloxane, boron nitride, melamine,a processing aid, and a ceramic. In specific embodiments the formulationcomprises, by weight fraction: from about 0.1 to about 50 percent boronnitride; from about 0.05 to about 0.10 percent melamine; from about 0.05to about 0.1 percent the processing aid and the ceramic combined; andthe remaining balance in specific embodiments is polydimethylsiloxane.

In specific embodiments one or more or any of the formulations describedherein can have one or more of: alkyds, polyisobutylene, epoxy resin orresins, polyurethanes (foams), and polycycloolefins.

In other specific embodiments of systems and methods described hereinthe battery pack comprises Lithium-Ion cells. Embodiments can alsocomprise prismatic pouch and/or can-type cells.

Specific systems and methods described herein can comprise shakingand/or vibrating the system to distribute the conformable thermalinterface material. For example in specific embodiments the shakingand/or the vibrating can be performed after the placing of theconformable thermal interface material into the support structure andbefore the cross-linking. In specific embodiments the cross-linking isperformed, thus decreasing of the flowability of the conformable thermalinterface material. In specific embodiments the decrease in flowabilityis such that the cross-linked thermal interface material forms a solidand in specific embodiments can provide support structure for thebattery pack. As used herein, a solid would refer to a completecross-linking of the liquid or gel such that a solid forms, and wouldindicate a fully cured liquid or gel. In specific embodiments, measureof cure is measured by sampling the material and testing on a nuclearmagnetic resonance machine to give a degree of cure. Flow-ability can beperformed before the material is cross linked with a dynamic mechanicalanalyzer.

In yet other specific embodiments of systems and methods describedherein a release liner can be placed on the reservoir. In specificembodiments the release liner is placed on the reservoir prior to theplacing of the conformable thermal interface material onto the top ofthe coolant reservoir and/or into and/or on the support structure. Inyet other specific embodiments, systems and methods described hereincomprise the conformable thermal interface material being physicallyremovable from the system and/or the release liner (either directly awayfrom the release liner or the release liner itself being removable fromthe system with the conformable thermal interface), and/or the step ofremoving the thermal interface and/or the release liner (such as a thinpolymer film or films, for example in specific embodiments one ore moreof polyethylene, or polyethylene terephthalate). In specific embodimentsthe release liner is about 100 micrometers in thickness, and in otherembodiments it is from about 75 to about 125 micrometers thick. Theremovability could be for service involving one or more of the cells.

Specific embodiments provided herein include a polymer matrix. As usedherein, polymer matrix refers to a mixture with polymers.

Specific embodiments use one or more methods or parts of systemsdescribed herein in combination with one or more of an acrylic baseceramic or silicone base.

1. A system for providing an even distribution of waste heat in avehicular battery pack comprising: the battery pack; at least one coldplate extending between two cells of the battery pack; a coolantreservoir coupled to the cold plate via a conformable thermal interfacematerial such that heat can be conducted therebetween; a supportstructure between the battery pack and the coolant reservoir; and theconformable thermal interface material in the form of a liquid or a gelplaceable within the support structure configured to be flowable so asto fill space between the reservoir and each cell of the battery packsuch that there is constant thermal contact between an entire lowersurface of each of the cells of the battery pack and a top surface ofthe coolant reservoir, and wherein the conformable thermal interfacematerial maintains the constant thermal contact upon cross-linking,which decreases the flowability of the conformable thermal interfacematerial and provides for the even distribution of the waste heat viaconduction of the waste heat from each of the cells to the coolantreservoir. 2.-20. (canceled)
 21. A conformable thermal interfacematerial comprising: a thermally conductive admixture including athermally conductive ceramic within a polymer; and a conformable polymerthat is flowable prior to addition of the thermally conductiveadmixture, wherein the conformable thermal interface material isflowable for a first predetermined period of time after mixture of thethermally conductive admixture with the conformable polymer, and whereinthe conformable thermal interface material is resilient after the firstpredetermined period of time.
 22. The conformable thermal interfacematerial of claim 21, wherein the conformable thermal interface materialundergoes, during the first predetermined period of time, at least oneof cross-linking, polymerization, or solvent evaporation to therebyproduce resilience of the conformable thermal interface material. 23.The conformable thermal interface material of claim 21, furthercomprising a processing aid.
 24. The conformable thermal interfacematerial of claim 23, wherein the processing aid is a fluorosurfactant.25. The conformable thermal interface material of claim 24, wherein thefluorosurfactant is perfluorononanoic acid.
 26. The conformable thermalinterface material of claim 21, wherein the conformable polymer isselected from the group consisting essentially of polyvinylidenefluoride, poly(di-methyl siloxane), polyurethane, unsaturatedpolyesters, alkyds, epoxies, polycycloolefins, and copolymers thereof.27. The conformable thermal interface material of claim 21, wherein thepolymer is selected from the group consisting essentially of silicones,epoxies, alkyd resins with a styrene solvent, polyvinylidene fluoridecopolymers, glues, polyoctenamers, or combinations thereof.
 28. Theconformable thermal interface material of claim 27, wherein the polymeris present in an amount between 50 wt % and 95 wt % on a basis of totalweight of resin solids.
 29. The conformable thermal interface materialof claim 21, wherein the thermally conductive ceramic is selected fromthe group consisting essentially of boron nitride, alumina, andsynthetic diamond.
 30. The conformable thermal interface material ofclaim 21, wherein the thermally conductive ceramic is present in anamount between 0.1 wt % and 50 wt % on a basis of total weight of resinsolids.
 31. The conformable thermal interface material of claim 21,further comprising an electrically conductive powder in an amount suchthat the conformable thermal interface material is electricallyconductive.
 32. The conformable thermal interface material of claim 21,wherein the conformable thermal interface material includes a thermalconductivity of at least about 2.5 Watt/m·K.
 33. The conformable thermalinterface material of claim 21, wherein the conformable polymer iscross-linked.
 34. The conformable thermal interface material of claim21, further comprising a polymer matrix defined by the conformablepolymer, the polymer matrix including the thermally conductive ceramicdispersed therein.
 35. The conformable thermal interface material ofclaim 21, wherein the conformable thermal interface material, on a basisof solids in the conformable thermal interface material, includes: thethermally conductive admixture in an amount from 5 wt % to 50 wt %; andand the balance being the conformable polymer in an amount from 50 wt %to 95 wt %.
 36. The conformable thermal interface material of claim 21,wherein the polymer and the conformable polymer both consist of the samematerial.
 37. The conformable thermal interface material of claim 21,wherein the conformable thermal interface material is flowable untilcross-linking of the conformable polymer.
 38. The conformable thermalinterface material of claim 21, wherein the thermally conductiveadmixture is present in an amount from 75 wt % to 90 wt % on a basis ofsolids in the conformable thermal interface material.
 39. Theconformable thermal interface material of claim 31, wherein theelectrically conductive powder is graphite, carbon black, aluminum,copper, zinc, silver, or mixtures thereof.